KR102022690B1 - Method for preparing of polarizer protecting film - Google Patents

Abstract

The present invention relates to a method for producing a polarizer protective film. More specifically, the present invention relates to a method for producing a polarizer protective film that can exhibit excellent physical and optical properties and can prevent damage to the lower polarizing plate by a prism sheet.

Description

Method for preparing polarizer protective film {Method for preparing of polarizer protecting film}

The present invention relates to a method for producing a polarizer protective film. More specifically, the present invention relates to a method of manufacturing a polarizer protective film that can exhibit excellent physical and optical properties and can prevent damage to the lower polarizing plate.

Liquid crystal display (LCD) is one of the most widely used flat panel display. In general, a liquid crystal display device has a structure in which a liquid crystal layer is enclosed between a TFT (Thin Film Transistor) array substrate and a color filter substrate. When an electric field is applied to the electrodes present on the array substrate and the color filter substrate, the arrangement of the liquid crystal molecules of the liquid crystal layer enclosed therebetween is changed, and an image is displayed using the same.

In the liquid crystal display device, since the light emitted from the light source passes through the light guide plate and the diffusion sheet, the luminance decreases, and thus the prism sheet is usually included in order to collect the light and increase the luminance. It is provided at the bottom. However, as the display is enlarged, sagging of the lower polarizing plate occurs, and damage occurs such that the lower polarizing plate is ground by the uneven structure of the prism sheet in contact with the lower polarizing plate. In order to solve this problem, a method of coating a hard coat layer on the protective film of the lower polarizer has been proposed, but there is a problem of an increase in process cost.

In accordance with such a necessity, there is still a need for development of a method for securing productivity and preventing price damage in the lower polarizing plate and increase of haze by the prism sheet while achieving price competitiveness in mass production.

In order to solve the above problems, the present invention is to solve the problem that the lower protective film of the polarizing plate is damaged, it is designed to provide a thin and scratch-resistant polarizer lower protective film, the present invention has excellent physical and optical properties It provides a method for producing a polarizer protective film that can be represented.

In order to solve the above problems, the present invention,

Applying a cationic curable coating composition on at least one side of the polymer film;

Stretching the polymer film to which the coating composition is applied; And

Performing photocuring on the coating composition,

It provides a method for producing a polarizer protective film.

According to the manufacturing method of the polarizer protective film of this invention, it can provide the polarizer protective film which has thinness and sufficient scratch resistance with high productivity, and a polarizing plate containing the same.

In addition, the lower protective film of the polarizing plate may be damaged due to the irregularities of the prism sheet provided on the lower part of the polarizing plate, thereby increasing the haze, and preventing a part of the damaged film from coming out as a foreign material and causing defects, thereby exhibiting excellent optical properties. have.

In addition, since such an effect can be obtained by applying the present invention to the lower polarizer of the LCD without changing such a laminated structure of the LCD, it is possible to reduce production costs without requiring excessive process change or cost increase.

1 is a diagram illustrating a liquid crystal display according to an embodiment of the present invention.

Method for producing a polarizer protective film of the present invention, the step of applying a cationic curable coating composition on at least one side of the polymer film; Stretching the polymer film to which the coating composition is applied; And performing photocuring on the coating composition.

In the present invention, the term 'top surface' refers to a surface that is disposed to face the viewer when the polarizer is mounted on a device such as a liquid crystal display. In addition, when the polarizer is mounted on the device, it means the direction toward the viewer. Conversely, 'bottom' or 'bottom' refers to a face or direction disposed so as to face away from the viewer when the polarizer is mounted on the device.

As the invention allows for various changes and numerous modifications, particular embodiments will be illustrated and described in detail below. However, this is not intended to limit the present invention to the specific disclosed form, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

Hereinafter, the manufacturing method of the polarizer protective film of this invention is demonstrated in detail.

According to one embodiment of the invention, the step of applying a cationic curable coating composition on at least one side of the polymer film; Stretching the polymer film to which the coating composition is applied; And it provides a method for producing a polarizer protective film comprising the step of performing a photocuring for the coating composition.

The polarizer exhibits the property of extracting only the light vibrating in one direction from the incident light while vibrating in various directions, and the polarizer protective film of the present invention is used for protecting the polarizer from the outside, and at least On one side, it is preferably used as the lower protective film of the polarizer.

On the other hand, as the display gradually increases in size, deflection of the lower polarizer may occur, and a protective film of the lower polarizer may be damaged by a prism sheet or a diffusion film provided below the lower polarizer, thereby increasing haze.

The present invention is to compensate for this problem, and to improve the scratch resistance of the polarizer protective film of the lower polarizing plate by improving the polarizing plate, especially the lower polarizing plate of the components included in the LCD without changing the structure of the backlight, color filter or LCD It is for preventing the problem of haze increase by a prism sheet or a diffusion film by including the extending | stretching coating layer which has.

Thus, the polarizer protective film obtained by the manufacturing method of the present invention exhibits excellent physical properties such as scratch resistance and high hardness due to the stretch coating layer effectively protects the lower polarizing plate, and is useful for a polarizing plate for display that is thinner and larger in size. Applicable

Polarizer protective film prepared according to an embodiment of the present invention is a polymer stretched film; And a stretch coating layer formed on one surface of the polymer stretched film.

The polymer stretched film is generally usable as a base film of a polarizer protective film and is not particularly limited as long as it is a stretchable film. For example, polyester, polyethylene, cyclic olefin polymer, COP), cyclic olefin copolymer (COC), polyacrylate (PAC), polycarbonate (PC), polymethylmethacrylate (PMMA), or polyimide (polyimide) PI) can be used.

The thickness of the polymer stretched film is not particularly limited, but a substrate having a thickness of about 50 to about 1,000 µm, or about 100 to about 500 µm may be used in consideration of the subsequent stretching process.

In addition, the molding method of the polymer film is also not particularly limited, and for example, the unstretched polymer film may be prepared by a suitable film forming method such as solution casting, melt extrusion, calendering, compression molding, or the like.

Conventionally, a triacetylcellulose (TAC) film has been used as a polarizer protective film because of its excellent optical properties. However, since the TAC film has a weak surface hardness and is vulnerable to humidity, in recent years, polyester films, polyacrylate films, etc. have been used instead of TAC films, and in particular, in order to develop optical films having excellent mechanical properties, The film produced is used a lot.

On the other hand, in the case of the stretched film, when the polymer is rearranged in the stretching process to further form a functional coating layer on the stretched film, there is a problem in that the adhesion is reduced. Therefore, there is a method of adding a separate process, such as forming a primer layer to secure the adhesion, or to include a functional compound that can improve the adhesion to the coating layer, in this case, a separate process is added in the manufacturing process to productivity There is a falling problem, and the physical and chemical properties of each film is different, it is difficult to develop a universal primer. In addition, adding a functional compound to the coating layer may also be a problem of increased cost and other physical properties.

Accordingly, the present invention solves this problem, according to an embodiment of the present invention, even if there is no separate primer layer, the adhesion with the stretched film to be a base material has a high scratch resistance, sufficient polarizer protection that can be thinned It is possible to provide a film.

According to an embodiment of the present invention, the polymer film may be coated with a coating composition on one surface thereof in an unstretched state.

Alternatively, according to another embodiment of the present invention, the polymer film may be uniaxially stretched before applying the coating composition.

At this time, the stretching direction is not particularly limited, and the stretching ratio may be stretched to be 1.1 times or more, 1.2 times or more, or 1.5 times or more, 5 times or less, or 3 times or less based on the length of the stretching direction.

A cationically curable coating composition is applied on at least one side of the unstretched or uniaxially stretched polymer film.

Generally, in order to form a functional coating layer such as a hard coating layer on the polarizer protective film, a method of applying, drying and curing the coating composition on the stretched film is used. However, in the case of the stretched film, since the polymer is rearranged in the stretching process, the coating layer does not adhere well to the stretched film. Although there is a method of forming a primer layer to secure adhesion, there is a problem in that productivity is reduced due to the addition of a separate process in the manufacturing process, and there is a problem in that general purpose primer development is difficult.

According to the production method of the present invention, after coating and stretching the coating composition on the polymer film, by curing the coating composition to form a coating layer, adhesion to the polymer stretched film without the need for a separate primer layer This high and thinning polarizer protective film can be provided.

On the other hand, if the coating composition is too rigid (rigid), there is a problem that the coating layer is uneven or not drawn properly in the stretching process after coating, on the contrary, if the coating composition is flexible and the elongation is too high, sufficient strength after coating and curing And scratch resistance may not be secured.

Therefore, in order to exhibit a uniform stretching process and sufficient scratch resistance after curing, it is important to appropriately balance the flexibility and strength of the coating composition with the stretching ratio of the polymer film.

Thus, according to the production method of the present invention, it is possible to provide a polarizer protective film that satisfies the above requirements by optimizing the composition and the stretching process of the coating composition.

In order to form a coating layer of the polarizer protective film, a radical curable binder such as an acrylate binder is mainly used. By the way, the radical curable resin is used for the purpose of forming a high hardness coating layer due to its high degree of curing, but the shortening of the crosslinking distance causes a hardening shrinkage phenomenon, resulting in deterioration of adhesion to the base film, or curling or cracking of the coating layer. The phenomenon occurs easily.

However, according to the present invention, instead of using a radically curable binder having a large curing shrinkage, such as an acrylate-based binder, a coating composition containing a cationic curable binder as a main component, and performing an stretching process after application of the coating composition It is possible to significantly reduce the adhesion with the base film due to curing shrinkage and curling and / or cracking of the coating layer. Therefore, a protective film having high adhesion between the coating layer and the base film and satisfying flexibility and hardness at the same time can be produced.

The cationic curable coating composition coated on the polymer film, the cation curable binder containing an epoxy compound; And cationic polymerization initiators.

According to one embodiment of the present invention, the weight average molecular weight of the epoxy compound is not particularly limited, but may have a range of about 100 to about 5,000 g / mol, or about 200 to about 5,000 g / mol, for example. have. If the weight average molecular weight is too large, the coating may not be good due to the viscosity is high, and if the weight average molecular weight is too small, the hardness may decrease, from this point of view, the weight average molecular weight of the cation-curable binder is preferably in the above range. .

The epoxy compound is a binder containing at least one epoxy group, the curing is initiated by the cation generated from the cationic polymerization initiator by ultraviolet irradiation, aromatic epoxy compound, hydrogenated epoxy compound, alicyclic epoxy compound And an aliphatic epoxy compound, and the like, and preferably an alicyclic epoxy compound can be used.

The aromatic epoxy compound means an epoxy compound including at least one aromatic hydrocarbon ring in a molecule, but is not limited thereto, for example, diglycidyl ether of bisphenol A and diglycidyl ether of bisphenol F Bisphenol-type epoxy resins such as diglycidyl ether of bisphenol S; Glycidyl ether of tetrahydroxyphenyl methane, Glycidyl ether of tetrahydroxy benzophenone, Novolak-type epoxy resin, such as a phenol novolak epoxy resin, a cresol novolak epoxy resin, and a hydroxy benzaldehyde phenol novolak epoxy resin, And polyfunctional epoxy resins such as epoxidized polyvinylphenol.

In addition, the hydrogenated epoxy compound means an epoxy compound obtained by selectively hydrogenating the aromatic epoxy compound in the presence of a catalyst under pressure, but is not limited thereto, and particularly among the hydrogenated bisphenol A Preference is given to using diglycidyl ether.

In addition, the alicyclic epoxy compound means an epoxy compound in which an epoxy group is formed between two adjacent carbon atoms constituting an aliphatic hydrocarbon ring, but is not limited thereto. For example, 2- (3, 4-epoxy) cyclohexyl-5,5-spiro- (3,4-epoxy) cyclohexane-m-dioxane, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, 3,4 -Epoxy-6-methylcyclohexylmethyl-3,4-epoxy-6-methylcyclohexanecarboxylate, vinylcyclohexanedioxide, bis (3,4-epoxycyclohexylmethyl) adipate, bis (3,4 -Epoxy-6-methylcyclohexylmethyl) adipate, exo-exobis (2,3-epoxycyclopentyl) ether, endo-exobis (2,3-epoxycyclopentyl) ether, 2,2-bis [4 -(2,3-epoxypropoxy) cyclohexyl] propane, 2,6-bis (2,3-epoxypropoxycyclohexyl-p-dioxane), 2,6-bis (2,3-epoxyprop Foxy) norbornene, limonene dioxide, 2,2-bis (3,4-epoxycyclohexyl) propane, dicyclopentadiene dioxide, 1,2-epoxy-6- (2,3-epoxypropoxy) Hexahydro-4,7-methanoindan, p- (2,3-epoxy) cyclopentylphenyl-2,3-epoxypropylether, 1- (2,3-epoxypropoxy) phenyl-5,6-epoxy Hexahydro-4,7-methanoindan, o- (2,3-epoxy) cyclopentylphenyl-2,3-epoxypropylether), 1,2-bis [5- (1,2-epoxy) -4 , 7-hexahydromethanoindanoxyl] ethanecyclopentenylphenylglycidyl ether, methylenebis (3,4-epoxycyclohexane) ethyleneglycoldi (3,4-epoxycyclohexylmethyl) ether, ethylenebis (3 , 4-epoxycyclohexanecarboxylate), ε-caprolactone (1-10 moles) adduct of 3,4-epoxycyclohexane methanol and polyvalent (3-20 values) alcohols (GR, TMP, PE, DPE And esterified compounds of hexapentaerythritol). Especially, it is preferable to use 3, 4- epoxycyclohexyl methyl-3, 4- epoxy cyclohexane carboxylate from a reactive viewpoint.

According to an embodiment of the present invention, the cation-curable coating composition may further include an oxetane-based compound as a cation-curable binder.

The oxetane-based compound is a binder including at least one or more oxetane groups, and curing is initiated by a cation generated from a cationic polymerization initiator by ultraviolet irradiation, and can be used without particular limitation.

The oxetane-based compound may lower the viscosity of the cationically curable composition, and may further improve the curing rate.

The oxetane-based compound is more specifically, for example, 3-ethyl-3-[(3-ethyloxetan-3-yl) methoxymethyl] oxetane, 1,4-bis [(3-ethyloxetane- 3-yl) methoxymethyl] benzene, 1,4-bis [(3-ethyloxetan-3-yl) methoxy] benzene, 1,3-bis [(3-ethyloxetan-3-yl) meth Methoxy] benzene, 1,2-bis [(3-ethyloxetan-3-yl) methoxy] benzene, 4,4'-bis [(3-ethyloxetan-3-yl) methoxy] biphenyl, 2,2'-bis [(3-ethyloxetane-3-yl) methoxy] biphenyl, 3,3 ', 5,5'-tetramethyl-4,4'-bis [(3-ethyloxetane -3-yl) methoxy] biphenyl, 2,7-bis [(3-ethyloxetan-3-yl) methoxy] naphthalene, bis {4-[(3-ethyloxetan-3-yl) meth Methoxy] phenyl} methane, bis {2-[(3-ethyloxetan-3-yl) methoxy] phenyl} methane, 2,2-bis {4-[(3-ethyloxetan-3-yl) meth Methoxy] phenyl} propane, etherified modified product of novolak type phenol-formaldehyde resin with 3-chloromethyl-3-ethyloxetane, 3 (4), 8 (9) -bis [(3-ethyloxetane -3-yl) methoxymethyl] -tricyclo [5.2 .1.0 2,6] decane, 2,3-bis [(3-ethyloxetan-3-yl) methoxymethyl] norbornane, 1,1,1-tris [(3-ethyloxetane-3- Yl) methoxymethyl] propane, 1-butoxy-2,2-bis [(3-ethyloxetan-3-yl) methoxymethyl] butane, 1,2-bis {[2- (3-ethyljade Cetane-3-yl) methoxy] ethylthio} ethane, bis {[4- (3-ethyloxetan-3-yl) methylthio] phenyl} sulfide, 1,6-bis [(3-ethyloxetane 3-yl) methoxy] -2,2,3,3,4,4,5,5-octafluorohexane etc. are mentioned.

According to one embodiment of the invention, 3-ethyl-3- (hydroxymethyl) oxetane, m-tetramethyl-xylene diisocyanate azeolaoyl chloride, terephthaloyl chloride and 1,3,5-benzene Compounds obtained by reaction with one or more compounds selected from the group comprising tricarbonyl trichloride can be used.

When the oxetane-based compound is further included, the content thereof may be about 5 to about 80 parts by weight, preferably about 10 to about 60 parts by weight, based on 100 parts by weight of the epoxy compound. If the oxetane-based compound is included too much, the hardness of the coating layer may decrease after curing, and if it is included too little, the effect of the addition of the oxetane-based compound is insignificant.

The cationic curable coating composition includes a cationic polymerization initiator.

The cationic polymerization initiator refers to a compound that generates a cation species or Lewis acid by irradiation of an active energy ray such as ultraviolet rays and acts on a cationic polymerizable group such as an epoxy group to initiate a cationic polymerization reaction.

In this case, as the cationic polymerization initiator, cationic polymerization initiators generally used in the art may be used without limitation. For example, a sulfonium salt or an iodonium salt may be preferably used as the cationic polymerization initiator.

Specific examples of the cationic polymerization initiator containing sulfonium salt or iodonium salt include, for example, diphenyl (4-phenylthio) phenylsulfonium hexafluoroantimonate (Diphenyl (4- phenylthio) phenylsulfonium hexafluoroantimonate), diphenyl (4-phenylthio) phenylsulfonium hexafluorophosphate (Diphenyl (4-phenylthio) phenylsulfonium hexafluorophosphate), (phenyl) [4- (2-methylpropyl) phenyl] -iodium hexa Fluorophosphate ((phenyl) [4- (2-methylpropyl) phenyl] -Iodonium hexafluorophosphate), (thiodi-4,1-phenylene) bis (diphenylsulfonium) dihexafluoroantimonate ((Thiodi- 4,1-phenylene) bis (diphenylsulfonium) dihexafluoroantimonate) and (thiodi-4,1-phenylene) bis (diphenylsulfonium) dihexafluorophosphate ((Thiodi-4,1-phenylene) bis (diphenylsulfonium) dihexafluorophosphate) and one or more selected from the group consisting of, but not limited thereto. Is not.

The amount of the cationic polymerization initiator may be about 0.1 to about 10 parts by weight, preferably about 0.1 to about 5 parts by weight, based on 100 parts by weight of the total cationically curable binder.

According to one embodiment of the invention, the coating composition may further comprise a thermosetting binder, and a thermal polymerization initiator. When the coating composition includes a thermosetting binder, a thermosetting process may be added during curing of the coating composition.

The cationically curable coating composition of the present invention can be used in a solvent-free type without solvent because of its low viscosity and good coating properties. However, the use of organic solvents is not excluded, and organic solvents commonly used in the art may be used in small amounts, for example, in an amount of about 20 parts by weight or less based on 100 parts by weight of the total coating composition. It may be.

Organic solvents that can be used include alcohol solvents such as methanol, ethanol, isopropyl alcohol, butanol, alkoxy alcohol solvents such as 2-methoxyethanol, 2-ethoxyethanol, 1-methoxy-2-propanol, acetone, Ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, methyl propyl ketone, cyclohexanone, propylene glycol monopropyl ether, propylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether Ether solvents such as diethylene glycol monomethyl ether, diethyl glycol monoethyl ether, diethyl glycol monopropyl ether, diethyl glycol monobutyl ether, diethylene glycol-2-ethylhexyl ether, benzene, toluene, xylene Aromatic solvents such as these may be used alone or in combination.

Meanwhile, according to one embodiment of the present invention, the coating composition may further include organic fine particles or inorganic fine particles to improve the hardness of the stretched coating layer. The particle diameter of the organic or inorganic fine particles may be 10 μm or less in terms of proper haze and coating thickness, and more specifically, about 10 nm to about 10 μm, preferably about 50 nm to about 5 μm, more preferably Particles from about 100 nm to about 3 μm.

As long as the said organic or inorganic fine particle is a kind used for forming the coating layer of an optical film, it can use without a limitation in the structure.

For example, the organic fine particles may be used one or more selected from organic fine particles composed of acrylic resin, styrene resin, epoxy resin and nylon resin.

More specifically, the organic fine particles are methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth ) Acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, Polyethylene glycol (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, glycidyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, styrene, p- Methylstyrene, m-methylstyrene, p-ethylstyrene, m-ethylstyrene, p-chlorostyrene, m-chlorostyrene, p-chloromethylstyrene, m-chloromethylstyrene, styrenesulfonic acid, pt-butoxystyrene, mt-butoxystyrene, vinyl acete Nitrate, vinyl propionate, vinyl butyrate, vinyl ether, allyl butyl ether, allyl glycidyl ether, (meth) acrylic acid, maleic acid, unsaturated carboxylic acid, alkyl (meth) acrylamide, (meth) acrylonitrile and It may be one or more selected from the group consisting of (meth) acrylate, but the present invention is not limited thereto.

In addition, the organic fine particles may be polystyrene, polymethylmethacrylate, polymethylacrylate, polyacrylate, polyacrylate-co-styrene, polymethylacrylate-co-styrene, polymethylmethacrylate-co-styrene, Polycarbonate, polyvinyl chloride, polybutylene terephthalate, polyethylene terephthalate, polyamide, polyimide, polysulfone, polyphenylene oxide, polyacetal, epoxy resin, phenol resin, silicone resin, melamine resin, benzogu At least one selected from amine, polydivinylbenzene, polydivinylbenzene-co-styrene, polydivinylbenzene-co-acrylate, polydiallylphthalate and triallyl isocyanurate polymer or two or more co Although a polymer may be used, the present invention is not limited thereto.

The inorganic fine particles may be one or more selected from the group of inorganic fine particles consisting of silicon oxide, titanium dioxide, indium oxide, tin oxide, zirconium oxide, and aluminum oxide, but the present invention is not limited thereto.

The total content of the organic and inorganic fine particles may range from about 0.1 to about 20 parts by weight, preferably about 1 to about 10 parts by weight, based on 100 parts by weight of the cationically curable coating composition. When the total content of the organic and inorganic fine particles is included in less than 0.1 parts by weight with respect to 100 parts by weight of the cation-curable composition, the effect of improving the hardness and scratch resistance is insignificant, and when it exceeds 20 parts by weight, the viscosity of the coating composition Higher coating properties and poor haze values due to internal scattering may result in a lower contrast ratio.

On the other hand, the coating composition of the present invention, in addition to the above-mentioned components, surfactants, antioxidants, UV stabilizers, leveling agents, antifouling agents, antistatic agents, UV absorbers, antifoaming agents, preservatives, etc. commonly used in the technical field to which the present invention belongs It may further include an additive. In addition, since the content can be variously adjusted within a range that does not lower the physical properties of the coating composition of the present invention, it is not particularly limited, for example, may be included in about 0.1 to about 10 parts by weight based on 100 parts by weight of the total coating composition. have.

The method of applying the coating composition is not particularly limited as long as it can be used in the art, for example, bar coating method, knife coating method, roll coating method, blade coating method, die coating method, micro gravure coating Method, comma coating method, slot die coating method, lip coating method, or solution casting method may be used.

Next, the polymer film coated with the coating composition is stretched.

The stretching direction is not particularly limited, and the stretching ratio is 1.05 times or more, or 1.2 times or more, or 1.5 times or more, 10 times or less, or 5 times or less, or 3 times or less based on the length of the stretching direction. Can be. When the draw ratio is less than 1.05 times, the effect of stretching may not be sufficiently achieved, and when the draw ratio is more than 10 times, the coating layer may be cracked, and it is preferable to draw in the draw ratio described above in this respect.

If the polymer film is uniaxially stretched before the coating composition is applied, the stretching direction after the coating is preferably stretched in a direction perpendicular to the stretching direction before the coating composition is applied. For example, if the polymer film is stretched in the length (MD) direction before the coating composition is applied, the polymer film may be stretched in the width (TD) direction after the coating composition is applied.

In addition, when stretching before and after applying the coating composition, the total draw ratio is 1.1 times or more, or 1.2 times or more, or 1.5 times or more, 25 times or less, or 10 based on the total stretching area of the polymer film. It can extend | stretch so that it may become less than twice or seven times or less. When the draw ratio is less than 1.1 times, the effect of stretching may not be sufficiently achieved, and when the draw ratio is more than 25 times, the coating layer may be cracked, and it is preferable to draw in the draw ratio described above from this point of view.

Before the stretching, the coating surface of the coating composition may be flattened, and a process of drying to volatilize the solvent included in the coating composition may be further performed.

Next, the stretched coating layer may be formed by irradiating the applied coating composition with ultraviolet rays to perform a photocuring reaction. The irradiation amount of ultraviolet rays may be, for example, about 20 to about 800 mJ / cm ² . The ultraviolet light source is not particularly limited as long as it can be used in the art to which the present technology belongs, and for example, a high pressure mercury lamp, a metal halide lamp, a black light fluorescent lamp, or the like can be used.

The polarizer protective film of the present invention obtained by the above process includes a polymer stretched film and a stretch coating layer formed on at least one surface of the polymer stretched film.

Since the stretch coating layer is integrated with the polymer stretched film and stretched, it is advantageous to provide a thin polarizer protective film having high adhesion with the polymer film serving as a substrate even without a separate primer layer.

According to one embodiment of the present invention, the stretch coating layer has a final thickness of about 100 nm or more, for example, about 100 nm or more, or about 500 nm or more, or about 1 μm or more after drying, stretching and curing. 20 μm or less, or about 10 μm or less, or about 5 μm or less, or about 3 μm or less. As described above, the stretched coating layer of the present invention may be manufactured in a thin form and may exhibit sufficient strength. In addition, even a single coating layer can exhibit sufficient hardness and scratch resistance, and exhibits high adhesion to the substrate without a primer layer, thereby increasing the workability and productivity of the manufacturing process.

The stretched coating layer may be formed only on one surface of the polymer stretched film, or may be formed on both sides of the polymer stretched film.

When the stretch coating layer is formed only on one surface of the polymer stretched film, the other surface may further include one or more other photocurable coating layers and / or thermosetting coating layers or other layers, films, or films for imparting functionality. have. It is also possible to further form another functional layer on the stretch coating layer.

As such, when the polarizer protective film of the present invention includes another layer, film, film, or the like on the other surface of the polymer stretched film, the formation method and step thereof are not limited. For example, a method of coating before stretching of the polymer film, stretching and curing, a method of coating and curing after stretching of the polymer film, a layer, film, or film formed separately may be applied to the polymer stretched film by using an adhesive or the like. Various methods known in the art, such as lamination, may be used to deposit another layer, film, or film on the other side of the stretched polymer film.

The polarizer protective film obtained by the manufacturing method of the present invention as described above, by measuring the haze (haze) change before and after reciprocating 10 times with a load of 100g after mounting steel wool (0000) to the friction tester The scratch resistance can be exhibited to such an extent that the haze change is 0.5 or less.

In addition, the polarizer protective film obtained by the production method of the present invention, the pencil hardness at 500g load may be H or more.

The polarizer protective film obtained by the above-described manufacturing method may be laminated on at least one surface of the polarizer to provide a polarizing plate including the same.

The polarizer exhibits a property of extracting only light vibrating in one direction from incident light while vibrating in various directions. This property can be achieved by stretching polyvinyl alcohol (PVA) absorbing iodine with strong tension. For example, more specifically, swelling by swelling the PVA film in an aqueous solution, dyeing with a dichroic substance imparting polarization to the swelled PVA film, stretching the dyed PVA film. The polarizer may be formed through a stretching step of arranging the dichroic dye materials side by side in the stretching direction, and a complementary color step of correcting the color of the PVA film subjected to the stretching step. However, the polarizing plate of the present invention is not limited thereto.

According to one embodiment of the present invention, the polarizer protective film may be attached to both sides of the polarizer.

According to another embodiment of the present invention, the polarizer protective film is provided only on one surface of the polarizer, and the other surface may be provided with a general protective film commonly used for polarizer protection.

In this case, the polarizing plate may be used as a lower polarizing plate of the LCD, and in the laminated structure in the LCD, the polarizer protective film of the present invention may be positioned below.

As described above, when the polarizing plate is laminated on the LCD with the polarizer protective film as the lower portion, the lower protective film of the polarizing plate is damaged due to the irregularities of the prism sheet or the diffusion film provided under the polarizing plate, thereby preventing the problem of increasing the haze, thereby providing excellent optical. It can exhibit physical properties.

The polarizer and the polarizer protective film can be bonded by lamination using an adhesive or the like. Usable adhesives are not particularly limited as long as they are known in the art. For example, there are water-based adhesives, one-component or two-component polyvinyl alcohol (PVA) adhesives, polyurethane adhesives, epoxy adhesives, styrene butadiene rubber (SBR) adhesives, or hot melt adhesives. It is not limited only to these examples.

When laminating and adhering the polarizer protective film of the present invention to the polarizer, it is preferable that the surface on which the stretch coating layer is not formed is attached to the polarizer, and the stretch coating layer is laminated so as to be positioned outward of the polarizing plate.

Such a polarizing plate having a protective film of the present invention has been described as an example to be applied to the LCD, but is not limited thereto, and may be utilized in various fields. For example, it can be used for mobile communication terminals, smart phones, other mobile devices, display devices, electronic blackboards, outdoor billboards, and various display units. According to an embodiment of the present invention, the polarizing plate may be a twisted nematic (TN), a super twisted nematic (STN) liquid crystal, an in-plane switching (IPS), a super-IPS, a fringe field switching (FFS), or the like. May be a polarizing plate for horizontal alignment mode, or may be a polarizing plate for vertical alignment mode.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the liquid crystal display containing the polarizer protective film obtained by the manufacturing method of this invention.

Referring to FIG. 1, the liquid crystal display device 1 may include a backlight unit 10; A prism sheet 20 provided on the backlight unit 10; And a polarizing plate 100 provided on the prism sheet 20 and laminated with the polarizer protective film 40 facing the prism sheet 20.

The backlight unit 10 includes a light source for irradiating light from the back of the liquid crystal panel, and the type of the light source is not particularly limited, and a general LCD light source such as CCFL, HCFL, or LED may be used.

The prism sheet 20 is provided on the backlight unit 10. Since the light emitted from the backlight unit 10 passes through the light guide plate and the diffusion sheet (not shown), the prism sheet 20 is lowered in brightness, and thus is provided to raise the brightness again. Such prism sheet 20 Is provided below the lower polarizer. However, since the prism sheet 20 includes a concave-convex structure, there is a problem in that the haze is increased by damaging the lower protective film of the lower polarizing plate which is in contact with the prism sheet 20.

However, the liquid crystal display device may improve this problem by stacking the polarizing plate 100 such that the stretch coating layer 30a of the polarizer protective film 40 faces the prism sheet 20.

That is, referring to FIG. 1, on the prism sheet 20, a general protective film 60 is provided on one surface of the polarizer 50, and the other surface includes a substrate 30b and a stretch coating layer 30a. A polarizing plate 100 having a polarizer protective film 40 of the present invention is provided, wherein the polarizer protective film 40 of the present invention is laminated to the lower side of the LCD, that is, toward the prism sheet 20. Has a structure. Due to such a laminated structure, the polarizing plate 100 may be damaged by the unevenness of the prism sheet 20, thereby preventing the problem of increasing haze and exhibiting excellent optical properties.

In addition, according to an embodiment of the present invention, a diffusion film or a dual brightness enhancement film (DBEF) between the prism sheet 20 and the polarizing plate 100 or between the backlight unit 10 and the prism sheet 20 (drawings) Not shown) may be further included. When the diffusion film or the DBEF film is positioned between the prism sheet 20 and the polarizing plate 100, the polarizer protective film 40 of the polarizing plate 100 is in contact with the diffusion film or the DBEF film, and in this case, the diffusion film or The problem of damage to the lower polarizing plate and increase of haze by the DBEF film or the like can be similarly prevented.

The layer provided on the polarizing plate 100 depends on the structure of a general liquid crystal display device. In FIG. 1, the lower glass substrate 70, the thin film transistor 75, the liquid crystal layer 80, the color filter 85, and the upper glass are illustrated in FIG. 1. Although the substrate 90 and the upper polarizer 95 are sequentially stacked, the LCD of the present invention is not limited thereto, and some of the layers shown in FIG. It may include any structure to which the substrate, film, sheet, etc. are added.

Hereinafter, the operation and effects of the invention will be described in more detail with reference to specific examples of the invention. However, these embodiments are only presented as an example of the invention, whereby the scope of the invention is not determined.

<Example>

Preparation of Coating Composition

Preparation Example 1

As a cation-curable binder, 6 g of Celloxide 2021P (Mw: 252.3 g / mol, Dicel), an alicyclic epoxy compound, 3 g of OXT-221 (Toyagosei), an oxetane compound, and a cation polymerization initiator CPI-100P (San-apro) 0.3g) was mixed to prepare a coating composition.

Preparation Example 2

As a cation-curable binder, 9 g of Celloxide 2021P, which is an alicyclic epoxy compound, and 0.3 g of a cationic polymerization initiator CPI-100P were mixed to prepare a coating composition.

Preparation Example 3

As a cation-curable binder, 6 g of Celloxide 2081 (Mw: 366.5 g / mol, Dicel), an alicyclic epoxy compound, 3 g of OXT-221, an oxetane compound, and 0.3 g of a cationic polymerization initiator CPI-100P were mixed to prepare a coating composition. It was.

Preparation Example 4

As a cation-curable binder, 6 g of an alicyclic epoxy compound (Ewpe 3150 (Mw: 4,000 g / mol, Dicel)), 3 g of oxetane compound OXT-221 and 0.3 g of a cationic polymerization initiator CPI-100P were mixed to prepare a coating composition. It was.

Preparation Example 5

As a cation-curable binder, 8 g of Celloxide 2021P, an alicyclic epoxy compound, 1 g of Eternacoll OXBP (Ube), an oxetane compound, and 0.3 g of a cationic polymerization initiator CPI-100P were mixed to prepare a coating composition.

Preparation Example 6

0.3 g of PMMA bead MX-800T (Soken) was further mixed with organic fine particles to the coating composition of Preparation Example 1 to prepare a coating composition.

Preparation Example 7

To the coating composition of Preparation Example 2 was further mixed with 0.6 g of silica (40 wt% dispersion in epoxy, average particle diameter of 10-20 nm, Ranco) as inorganic fine particles to prepare a coating composition.

Preparation Example 8

0.6 g of alumina (30 wt% dispersion in epoxy, average particle diameter of 10-20 nm, Ranco) was further mixed with the coating composition of Preparation Example 2 to prepare a coating composition.

Preparation Example 9

As a water-dispersible polyester / acrylic composite resin, 5.3 g of A645GH (30 wt% solids) of Takamatsu Oil & Fat, 0.4 g of silica (30 wt% dispersion in water, average particle diameter of 70-100 nm, Ranco) and 4.3 g of water were used as inorganic fine particles. Mixing prepared the coating composition.

Preparation Example 10

645 g of A645GH (30 wt% solids) of Takamatsu Oil & Fat, a water-dispersible polyester / acrylic composite resin, 1.6 g of CK-PUD-PF (30 wt% of solids) of dimmer paint, a water-dispersible polyurethane resin, and silica (water To 30wt% dispersion, average particle diameter 70 ~ 100nm, Ranco 0.4g, and 4.3g of water were mixed to prepare a coating composition.

Production Example of Polarizer Protective Film

Example 1

Polymethyl methacrylate resin using a T-die film forming machine under 250 ℃ conditions to prepare an unstretched film of width 800mm, thickness 200㎛. The unstretched film was stretched 1.8 times in the length (MD) direction at a temperature of 135 ° C. to prepare a uniaxially stretched film.

On the uniaxial stretched film, the coating composition of Preparation Example 1 was coated by a bar coating method, and then stretched 2.5 times in a width (TD) direction at a temperature of 135 ° C.

Ultraviolet rays were irradiated to prepare a polarizer protective film having a stretched coating layer having a thickness of 2 μm.

Examples 2-8

A polarizer protective film was prepared in the same manner as in Example 1 except that the coating compositions of Preparation Examples 2 to 8 were used instead of the coating compositions of Preparation Example 1, respectively.

Comparative Example 1

Polymethyl methacrylate resin using a T-die film forming machine under 250 ℃ conditions to prepare an unstretched film of width 800mm, thickness 200㎛. The stretched film was stretched 1.8 times in the length (MD) direction at a temperature of 135 ° C., and then stretched 2.5 times in the width (TD) direction at a temperature of 135 ° C. to prepare a stretched film.

On the stretched film, the coating composition of Preparation Example 1 was coated to a thickness of 2 μm by a bar coating method and then irradiated with ultraviolet rays to prepare a polarizer protective film having a coating layer.

Comparative Example 2

Except not forming a coating layer on the stretched film was prepared in the same manner as Comparative Example 1 and used as a polarizer protective film as it is.

Comparative Example 3

Polymethyl methacrylate resin using a T-die film forming machine under 250 ℃ conditions to prepare an unstretched film of width 800mm, thickness 200㎛. The unstretched film was stretched 1.8 times in the length (MD) direction at a temperature of 135 ° C. to prepare a uniaxially stretched film.

On the uniaxial stretched film, the coating composition of Preparation Example 9 was coated by a bar coating method, and then dried at a temperature of 100 ° C.

The polarizer protective film in which the extending | stretching coating layer whose thickness is 2 micrometers was formed by extending | stretching 2.5 times in the width | variety (TD) direction at the temperature of 135 degreeC was produced.

Comparative Example 4

A polarizer protective film was prepared in the same manner as in Comparative Example 3 except that the coating composition of Preparation Example 10 was used.

Experimental Example

<Measurement method>

Physical properties of the polarizer protective films of Examples and Comparative Examples were measured by the following methods.

1) Scratch resistance

After measuring the initial haze value on the surface of the coating layer of the polarizer protective film of the Example and the comparative example, the haze change was measured after rubbing 10 times with the load of Steel wool # 0000 100g. When the haze change value was 0.5 or less compared to the initial haze value, it was described as O when the haze change value was more than 0.5 and 1 or less, and when it exceeded 1, X was described. Haze value was measured using the Haze meter (HM 150).

2) adhesion

According to ASTM D3359, 100 (10x10) sheaths were cut and a tape (trade name: CT-24, manufacturer: Nichiban) was applied to the coating layers of the polarizer protective films of Examples and Comparative Examples so that the width and length were 1 mm, respectively. The number of coating layer compartments peeled off with the tape was counted.

O was 0 to 5 falling spaces, and X or more when 6 or more were evaluated.

3) pencil hardness

Pencil hardness was measured at a 500g load using a pencil hardness tester (hardness tester, manufacturer: Chungbuk Tech). According to ASTM 3363-74, while changing the standard pencil (Mitsubishi) from 6B to 9H while maintaining a 45 degree angle, the surface of the stretched coating layer was scratched to observe the change of the surface. Each experimental value is described as the average value after 5 measurements.

The physical property measurement results are shown in Table 1 below.

Scratch resistance Pencil hardness Adhesion Example 1 O 2H O Example 2 O 3H O Example 3 O 2H O Example 4 O H O Example 5 O 2H O Example 6 O 2H O Example 7 O 2H O Example 8 O 3H O Comparative Example 1 O H X Comparative Example 2 X HB Not applicable Comparative Example 3 X B O Comparative Example 4 X 2B O

Referring to Table 1, the polarizer protective film obtained according to the production method of the present invention showed excellent haze, scratch resistance, pencil hardness, and adhesion. However, Comparative Example 1 in which the coating layer was formed without the primer treatment on the stretched film was found to have poor adhesion.

The films of Comparative Example 3 in which the stretch coating layer was formed using the water-dispersed polyester / acrylic resin and Comparative Example 4 in which the water-dispersed polyester / acrylic resin and the water-dispersed polyurethane resin were mixed have insufficient scratch resistance and pencil hardness. It evaluated as not being suitable as a lower protective film of a polarizing plate.

Claims (9)

Uniaxially stretching the polymer film from 1.1 times to 3 times or less based on the length in the stretching direction;
Applying a cationic curable coating composition on at least one side of the polymer film;
Stretching the polymer film to which the coating composition is applied, at least 1.05 times to 3 times based on the length of the stretching direction in a direction perpendicular to the uniaxial stretching direction before application of the cationically curable coating composition; And
Performing photocuring on the coating composition,
The cation-curable coating composition is a cation-curable binder containing an epoxy compound; And a cationic polymerization initiator,
Method for producing a polarizer protective film.
delete The method of claim 1,
The polymer film, polyester (polyester), polyethylene (polyethylene), cyclic olefin polymer (cyclic olefin polymer, COP), cyclic olefin copolymer (cyclic olefin copolymer, COC), polyacrylate (polyacrylate, PAC), Polycarbonate (PC), and polymethylmethacrylate (polymethylmethacrylate, PMMA), polyimide (polyimide, PI) comprising at least one member selected from the group consisting of, a method for producing a polarizer protective film.
delete The method of claim 1,
The weight average molecular weight of the said epoxy compound is 100-5,000 g / mol, The manufacturing method of the polarizer protective film.
The method of claim 1,
The epoxy compound is a method of producing a polarizer protective film, which is an alicyclic epoxy compound.
The method of claim 1,
The cation-curable coating composition further comprises organic fine particles or inorganic fine particles, a method for producing a polarizer protective film.
The method of claim 1,
The cationically curable binder further comprises an oxetane-based compound.
delete

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